<!-- HTML5 metadata -->
{% if page.keywords %}
  <meta name="keywords" content="{{ page.keywords }}" />
{% elsif page.tags %}
  <meta name="keywords" content="{{site.author.name}}, {% if site.author.OtherName %}{{site.author.OtherName}}{% endif %}, {{ page.tags | join: ', ' }}" />
  {% assign page_keywords = page.tags %}
{% else %}
  <meta name="keywords" content="{{site.author.name}}, {% if site.author.OtherName %}{{site.author.OtherName}}{% endif %}, quantum optics, quantum information, quantum computing, quantum computation, 量子光学, 量子信息, 量子计算, 原子物理, atomic physics, blog, notebook, labnotebook, nanophotonics, 纳米光学" />
{% endif %}

{% if page.description %}
  <meta name="description" content="{{ page.description }}" />
  {% assign page_description = page.description %}
{% elsif page.subtitle %}
  <meta name="description" content="{{ page.subtitle }}" />
  {% assign page_description = page.subtitle %}
{% else %}
  <meta name="description" content="{{ page.title }}" />
  {% assign page_description = page.title %}
{% endif %}

<meta http-equiv="Content-Language" content="en, zh-Hans, cmn">
<!-- RDFa Metadata (in DublinCore) -->
<meta property="dc:title" content="{{ page.title }}" />
<meta property="dc:creator" content="{{ site.author.name }}" />
<meta property="dc:date" content="{{ page.date }}" />
<meta property="dc:format" content="text/html" />
<meta property="dc:language" content="en" />
<meta property="dc:identifier" content="{{ site.purl }}{{ site.baseurl }}{{ page.url }}" />
<meta property="dc:rights" content="CC-BY" />
<meta property="dc:source" content="{{ site.title }}" />
<meta property="dc:subject" content="Physics" />
<meta property="dc:type" content="website" />
<meta name="dc.language" content="en, zh-Hans, cmn">
<!-- RDFa Metadata (in OpenGraph) -->
<meta property="og:title" content="{{ page.title }}" />
<meta property="og:author" content="{{site.purl}}{{ site.baseurl }}/index.html" />  <!-- Should be Liquid? URI? -->
<meta property="https://ogp.me/ns/profile#first_name" content="{{ site.author.givenName }}"/>
<meta property="https://ogp.me/ns/profile#last_name" content="{{ site.author.familyName }}"/>
<meta property="https://ogp.me/ns/article#published_time" content="{{ page.date }}" />
<meta property="og:site_name" content="{{ site.title }}" /> <!-- Same as dc:source? -->
<meta property="og:url" content="{{site.purl}}{{ site.baseurl }}{{ page.url }}" />
<meta property="og:type" content="website" />
<!-- Google Scholar Metadata -->
<meta name="citation_author" content="{{ site.author.name }}"/>
<meta name="citation_date" content="{{ page.date }}"/>
<meta name="citation_title" content="{{page.title}}"/>
<meta name="citation_journal_title" content="{{site.title}}"/>
<!--NOTE: see also the COinS Metadata in span element in coins.html and footer. -->
<!-- Twitter card summary -->
<meta name="twitter:card" content="summary" />
<meta name="twitter:site" content="@{{site.author.twitter}}" />
<meta name="twitter:title" content="{{ page.title }}" />
<meta name="twitter:description" content="{{ page.description }}" />
<meta name="twitter:image" content="{{ site.purl }}{{ site.baseurl }}/assets/img/qi2016.jpg" />
<!-- Baidu website verification code -->
<meta name="baidu-site-verification" content="{{site.baiduid}}" />
